21757232209 has 2 divisors, whose sum is σ = 21757232210. Its totient is φ = 21757232208.

The previous prime is 21757232201. The next prime is 21757232219. The reversal of 21757232209 is 90223275712.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21639292609 + 117939600 = 147103^2 + 10860^2 .

It is a cyclic number.

It is not a de Polignac number, because 21757232209 - 2³ = 21757232201 is a prime.

It is not a weakly prime, because it can be changed into another prime (21757232201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10878616104 + 10878616105.

It is an arithmetic number, because the mean of its divisors is an integer number (10878616105).

Almost surely, 2^21757232209 is an apocalyptic number.

It is an amenable number.

21757232209 is a deficient number, since it is larger than the sum of its proper divisors (1).

21757232209 is an equidigital number, since it uses as much as digits as its factorization.

21757232209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 105840, while the sum is 40.

The spelling of 21757232209 in words is "twenty-one billion, seven hundred fifty-seven million, two hundred thirty-two thousand, two hundred nine".